It is possible that EW/EH to change when the bandwidth of channel
S-parameters is changed. This is because the circuit simulation tool
approximates the out-of-band behavior. There is no control over the
accuracy of this behavior. There is more control on this accuracy the more
the bandwidth of channel S-parameters.
Given that EW/EH values can change with bandwidth, it is important to know
the magnitude of the change. What is the percentage of change in EW/EH
values do you see between 50 and 100 GHz?
Though some change is expected in EW/EH values, I feel the trend of the
change (i.e., whether EW/EH values increase/decrease with bandwidth) is not
always predictable. In your case, these values increase as bandwidth is
increased. This trend suggests that the out-of-band behavior (from the ckt.
simulator) seems to have more loss than the reality. This need not always
be the case.
The magnitude of change (in EW/EH values) will be large if the rise time is
small, especially if it is smaller than 20 ps (one over 50 GHz). If your
rise time is smaller than 20 ps, then I would trust the results with the
larger bandwidths more.
Finally, the out-of-band behavior is also a function of the approach used
to convert S-parameters to impulse responses (convolution vs. rational
functions). I feel convolution approaches can under-represent loss
out-of-band while the rational-function approaches can over-represent it.
Thus, the more bandwidth, the trend of the change can be different using
these approaches.
Subramanian
On Sun, Jul 21, 2019 at 3:30 PM Tramp <farhilltramper@xxxxxxxxx> wrote:
Dear SI experts,
It seems that the bandwidth of channel sparameter has influence on the eye
result.Taking 10GKR for example, when comparing the eye obtained w/ the snp
of the BW of 50GHz, 60GHz, and 100GHz, the trend I observed so far is as
follows:
The 50GHz snp gets the smallest EH + largest EW, and vice versa for the
100GHz snp. The eye obtained w/ 60GHz has the mediate EH/EW in between,
Does that make sense? If, anyone can explain why?
--
Best Regards,
Tramp
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